Communications devices include two different sets of communications hardware, a communications transmitter and a communications receiver. Usually, the communications transmitter and receiver co-reside in a common package and share many system components, such as a power supply or a signal input device, like an antenna or a transmission line. The communications transmitter is responsible for transmitting information while the communications receiver is responsible for receiving information. Both the communications transmitter and receiver can be of type wireless or wired and digital or analog. Typically, within a single communications device, both the transmitter and receiver will be of the same type.
Communications receivers, be they wireless or wired and digital or analog, require adjustments to internal hardware to optimize performance. One commonly used solution that allows optimizing communications receiver hardware is to use a training period during equipment power up or initialization of a communications link. During the training period, a communications transmitter will send a sequence of data, test signals, and test tones (commonly referred to as a training sequence) to the communications receiver via a communications channel and in some cases, the communications transmitter corresponding to the communications receiver will transmit its own sequence back to the communications receiver associated with the communications transmitter. The communications receiver will analyze the received training sequence and derive a set of adjustments for its hardware. The derivation is possible because the communications receiver knows a priori the sequence of data, test signals, and test tones that the communications transmitter is sending and is able to determine useful information about the received training sequence that it uses to optimize its hardware.
However, difficulties exist involving adjusting internal hardware for optimizing system performance. These difficulties revolve around fact that communications receivers are typically designed with one-way signal paths, where a received signal flows in a single direction after arriving at the communication receiver's antenna, light emitter/detector, transmission line, etc. and are then processed, manipulated and modified by various internal circuitry. Due to the changes imparted upon the received signal, by the time the received signal arrives at the communications receiver's controller, typically a microprocessor or a digital signal processor, the signal has become distorted or undergone so many modifications that it is very difficult to make an intelligent decision on the type of adjustments required to optimize the communication receiver's hardware which lay further back up the receive path.
The training sequence is useful in optimizing receiver hardware such as an equalizer. A receiver's equalizer is responsible for flattening the communications channel's frequency response so that the magnitude of the signal over a frequency band of interest is relatively constant, with no attenuation at the higher frequencies. However, internal data-rate mismatches resulting from conversion processes such as analog-to-digital conversions (which typically oversamples the signal by as much as 8 or more), prevent the receivers signal processors from using the training sequence for adjusting the analog-to-digital converter's dynamic range.
A need has therefore arisen for a solution that will permit a communications receiver to perform optimizations on its own hardware without requiring additional external hardware support.